The precise role that the basal ganglia may play in movement control remains unclear. Lesion studies in monkeys and studies of patients with Parkinson's disease and other movement disorders suggest that the basal ganglia, and in particular the striatum, may play a role in sensorimotor adaptation of the type seen following exposure to displacing (wedge) prisms. In order to help clarify the role that the basal ganglia may play in this and other types of adaptive motor behavior, this project will compare the effects of different types of basal ganglia dysfunction on three separate but related forms of sensorimotor adaptation, including adaptation to experimentally induced distortions of visual input, proprioceptive input, and motor effector output. There will be seven patient groups, including subjects with unilateral or bilateral Parkinson's disease, dystonia or chorea, and patients with Parkinson's disease who are scheduled to undergo therapeutic pallidotomy. These patient groups, as well age-and sex-matched control subjects, will be compared in terms of their respective capacities to adapt to prism displacements (Specific Aim 1), to cervical tendon vibration (Specific Aim 2), and to spatial rotations of effector output (Specific Aim 3). The pallidotomy patients will be tested before and after they undergo selective lesioning of the pallidal outflow portion of the basal ganglia skeletomotor circuit. Inclusion of these patients may permit us to determine whether the capacity for sensorimotor adaptation, if impaired in Parkinson's disease, can be restored by subsequent ablation of disordered pallidal outflow. In the first two studies, proprioceptive and visual components of the total adaptive response will be differentiated into their respective sub-components, including cranial shift, limb shift, ocular shift, and visual sensory shift. All three sets of experiments are designed to measure both the time course of the process of adaptation and the magnitudes of the induced adaptive shifts. It is expected that patients with lateralized disease will show lateralized impairments of all three forms of sensorimotor adaptation. It is also predicted that the proprioceptive component of sensorimotor adaptation may be differentially impaired in patients with basal ganglia disorders, in light of their well-documented difficulties in making targeted movements in the absence of visual feedback. The project as a whole is designed to help clarify the possible relationships among these various types of adaptive motor behavior, and to determine their respective dependencies upon the normal functioning of the basal ganglia.